Process for the manufacture of silicon steel



\ and the scope of the a is-b'rittle and Patented Aug. 19, 1930 PATENT OFFICE WILLIAM J. WOOLDBIDGE, OF MANSFIELD, OHIO raocnss non ran mmirhcruan or 'srmcon srnnr.

No Drawing.

This invention relates to a process for the" manufacture of silicon-steel in the form'of plates and sheets adapted for use in electrical apparatus, such as reactors, transformers, 5 and the lik r The invention has for its object generally the provision of an improved fprocess, for pro ducmg plates and sheets 0 the character specified, which have better mechanical and electrical properties than those heretofore manufactured, in a manner which is both eflicient and economical.

More particularly, an object of the invention is to reduce substantially to a minimum the scale which forms on siliconteel in the process of its manufacture, and a the same time to provide silicon-steel sheets or plates which have the properties of a well-filnealed steel. Y i Other objects of the invention wilf in part be obvious and will in part appear hereinafter. V

The invention accordingly comprises the 25 several steps and the relation and order of one or more of suchsteps with respect to I each of the others thereof, which will'be exemplified in the process hereinafter disclosed, plication of which will be indicated in the c aim.

Steel which has been rolled and given heat treatments is known to develop a film of oxides or scale over its surface. This scale or punchings om being manufactured with desired facllity.

- To. eliminate the undesirable effects of scale, pickling the plates and sheets has been proposed. This plckling removes the scale ance of the plates and sheets. After the pickling the sheets may again be rolled if are then plckled by'placing them in vats I rolling should be done before the pickling Application filed Kay 28,

tprevents the steel laminations and, as a rule, improves the surface appear- 1928. Serial, No. 280,953.

stage,and in order that the sheets and plates have desired magnetic properties, viz, low core losses and high permeability, they should be annealed again after the pickling.

In brief, in accordance with the present invention, the plates or sheets of silicon-steel are first hot-rolled, and then cold-rolled, after which they are annealed at the usual temperature for such material. After the sheets 'or plates have become cold,- they are then pickled and dried, and then re-annealed at a comparatively low temperature. When this cycle of operations is completed, the sheets and plates are ready for use. I

At the beginning of the cycle, heated plates or ingots are hot-rolled in any suitable mill,

hot rolling has been completed, the plates are allowed to cool, and then are cold-rolled in a finishingmill until the desired gauge is attained. When this rolling is completed, the grain is fully developed. After the plates orsheets have thus been fully rolled, they maybe comparatively hard and brittle. In the next step of the process the sheets or platesare iven their first an-. neal. This is accomplis ed. by heating the sheets and plates when placed in suitable groups -or stacks in the heating. chamber of any suitable furnace, for example, a muflle furnace which is heated substantially to the usual temperatures employed for silicon-steel sheets, i. e., to a temperature of about 700 to 800 degrees 0. Such temperature is held for a proper. period, for example, 4 to 8 hours, after which the furnace is permitted to cool and the sheets removed.

, After the first anneal, the sheets or plates where they aresubjected to a bath of highly may be effected by placing the sheets or plates sheet. Such scale contains arelatively high precentage of silicon oxide, (SiO,), and as a result is very hard and readily cracks. While the inner core of a silicon-steel sheet has been sheets are placed for a second time in an annealing furnacewhere they are heated to a comparatively lo temperature for siliconsteel anneals. This temperature may be, for example, 300 degrees C. This second anneal in the oven of a mufile furnace in suitable stacks and bringing them gradually up to thedesired temperature, and holdin the same at such temperature for about 4 ours,

after which the heat is shut off and the sheets allowed .gradually' to cool before they are brought again into the outer atmosphere.

' By the process of the resent invention the resannealed silicon stee sheets or plates possess desired electrical vand n'echanical properties in relatively high degrees.

The cold-rolling, prior'to the first anneal racticed as above described, provides for; the evelopment of adefinite ain in the metal without ingrainin into t e metal 'an sub: v

stantial-amount o refractory materia such as the'scale which has heretofore at times beeii rolled into the metal. Silicon-st e el sheets which contain this material have a bi h degree of'attrition, and, as a result, quick y wear out the ed es of dies and other tools designed for working and cutting the same into stampings.

By the process of the present invention silicon-steel s eets and plates are produced which are substantially free from scale, have a clear surface, possess a high de cc of malleability, and can be cut in punc presses with relatively little wear on the dies. The dies of steel which are employed in such instances have substantially'three times the life which they would have had cutting ordinary siliconsteel sheets and plates. Moreover, the grain of the metal initially developed is not lost duriplg the annealin steps practiced as herein taug t. and plates produced by the present process have relatively high electrical permeabilities and show relatively low hysteresis losses even when working up to'flux densities as high as 17 ,OOOgauss or lines per square centimeter,v

pickled, the plates or sheets are taken from t Silicon-steel plates and sheets, which have substantially the following composition by analysis:

Per cent Iron 99.00 to 95.00 Silicon; 0.5 to 4.50 Carbon 0.1 to .10 .Man aucsc Approx. .12

Sulp ur Approx. .03" Phosphorus Approx. .02

show, when tested for hysteresis losses in an Epstein testing apparatus,'losses of from 0.5 to 3.00 watts er pound at a frequency of 60 cycles and a ux density of 10,000 lines per square centimeter, depending upon the thickness of sis.

Since certain changes may be made in car- 'rying'out the above process without departing from the scope of the invention. it is intended that all matter contained in the above "description shall be interpreted as illustrative and not in a'limiting sense.

. Having described myinvention, what I claim as new and'desire to secure by Letters Patent is: I

The process of manufacturing silicon-steel sheets and plates, which com rises hot-rolling said sheets in a standard mill until within .a ew per cent. of their desired gauge, coldrolling the same in a'finishing mill until the desired gauge is attained, annealing the same at usual'tem'perature for such material, pickling and dr ing the same, and thereafter reannealing t e same at-a temperature not subplate or sheet as well as on the analystantiallygreater at any time than 300 deg'rees O.

In testimony whereof Iaflix my signature.

WILLIAM J. WOOLDRIDGE.

As a resu t the silicon-steel sheets CERTIFICATE or CORRECTION.

Patent No. 1,773, 151. Granted August '19, 1930, m.

WILLIAM J. WOOLDRIDGE.

, It is'hereby certified that errorappears in the printed specification of the above numbered patent requiring correction as follows: Page 2, line 72, in the table, for carbon ',0.l to ,10" read .01 to .10; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office;

Signed and sealed this 21st day of Octoiier, A. D. 1930.

l M. J. Moore, (Seal) ActingConmissioner of Patents. 

